Electronic Telegram No. 2625
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director: Daniel W. E. Green; Hoffman Lab 209; Harvard University;
20 Oxford St.; Cambridge, MA 02138; U.S.A.
e-mail: cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network
SUPERNOVA 2011B IN NGC 2655
H. Yamaoka, Kyushu University, reports the discovery by Koichi Itagaki
(Yamagata, Japan) of a possible supernova (mag 15.8) on an unfiltered CCD
image taken on Jan. 7.431 UT with a 0.30-m reflector at Takanezawa, Tochigi.
The new object was not detected on Itagaki's image taken on Jan. 2.447
(limiting mag 18.5), but it does appear at mag 17.5 on his image taken on
Jan. 5.570. The variable is located at R.A. = 8h55m48s.50, Decl. =
+78d13'02".7 (equinox 2000.0), which is 31".7 east and 21".4 south of the
nucleus of NGC 2655. Itagaki's discovery image can be seen at the following
website URL: http://www.k-itagaki.jp/images/psn2655.jpg. Yamaoka adds that
Ken-ichi Kadota (Ageo, Saitama, Japan) confirmed 2011B at mag 15.9 on
co-added images taken on Jan. 7.724 with a 0.25-m reflector, from which he
measured position end figures 48s.03, 01".5. Yamaoka also forwards a report
from M. Koishikawa, Sendai Astronomical Observatory (SAO), who notes that
2011B is not visible detected on a CCD image (limiting mag about 19.0) taken
on Jan. 3.735 UT with the SAO 1.3-m reflector.
S. Nakano, Sumoto, Japan, reports the independent discovery of 2011B
by Masaki Tsuboi (Kuchita-minami, Asakita-ku, Hiroshima) on a 30-s unfiltered
CCD frame limiting magnitude 17.5) taken on Jan. 8.459 UT using a 0.30-m
f/5.3 reflector (+ ST-2000XM camera); Tsuboi provides mag 15.7 and position
end figures 47s.87, 01".1 (offset 30".4 east and 22".9 south of the center
of NGC 2655). Nothing is visible at this position on Tsuboi's survey frames
taken on 2010 Dec. 31 and 2011 Jan. 4, or on a red Digitized Sky Survey image.
His discovery image is posted at the following website URL:
http://ftenku.web.fc2.com/astrophoto/NGC2655110108-02.jpg.
T. Yusa writes that he obtained three 120-s unfiltered CCD exposures of
2011B on Jan. 8.192 UT while remotely using a 0.25-m f/3.4 hyperbolic
astrograph (+ SBIG ST-10XME camera) at the RAS Observatory near Mayhill,
NM, U.S.A., yielding mag 15.4 and position end figures 48s.02, 01".0. His
image (limiting mag 20.5) has been posted at the following website URL:
http://www.palette.furukawa.miyagi.jp/space/images/PSNinN2655_110108.jpg.
After posting on the Central Bureau's unconfirmed-objects webpage, D. D.
Balam, Dominion Astrophysical Observatory, National Research Council of
Canada; M. L. Graham, Las Cumbres Observatory Global Telescope, University of
California at Santa Barbara; and E. Y. Hsiao, Lawrence Berkeley Laboratory,
report that a spectrogram (range 385-694 nm, resolution 0.3 nm) of 2011B,
obtained on Jan. 8.42 UT with the 1.82-m Plaskett Telescope of the National
Research Council of Canada, shows it to be a type-Ia supernova near maximum
light. Cross-correlation with a library of supernova spectra using the
"Supernova Identification" code (Blondin and Tonry 2007, Ap.J. 666, 1024)
indicates that 2011B is most similar to the type-Ia supernova 1992bo a few
days pre-maximum light.
NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
superseded by text appearing later in the printed IAU Circulars.
(C) Copyright 2011 CBAT
2011 January 9 (CBET 2625) Daniel W. E. Green